Re:

[Arkady <arkady dot miasnikov at gmail dot com>]

This link can be relevant
https://stackoverflow.com/questions/33718358/insmod-fails-with-unknown-symbol-in-module-for-a-symbol-defined-in-another-mod

On Sun, Jul 30, 2017 at 10:09 AM, Arkady <arkady.miasnikov@gmail.com> wrote:
> Daniel,
>
> STAP attempts to compile the kernel module against the kernel source
> tree installed in the system. One way to resolve the issue is to
> update the kernel source tree installed in the system. Without
> updating the kernel sources the compilation will fail.
>
> On Sun, Jul 30, 2017 at 9:56 AM, Daniel Doron <danielmeirdoron@gmail.com> wrote:
>> Hi,
>>
>> How is systemtap's kernel module different from other modules?
>> Given module A which exports a function and module B using that exported
>> function and A is insmodded before B, I have not seen any problem. Why is
>> Systemtap's KO different? Is it not the kernel's job to resolve the exported
>> symbol?
>>
>>
>> Daniel.
>>
>> On Thu, 27 Jul 2017 at 19:29 Arkady <arkady.miasnikov@gmail.com> wrote:
>>>
>>> P.S.1 There is yet another way - very cool way - to to add a symbol to
>>> the stap script - via /sys/kernel/debug/systemtap/<module name>/.cmd
>>> (CTL_CHANNEL_NAME below)
>>>
>>> This is a Python sample
>>>
>>> def write_relocate_string(f, s, size):
>>>     f.write(s)
>>>     padding = size - len(s)
>>>     for _ in range(padding):
>>>         f.write('\x00')
>>>
>>> def write_relocate(module_name, symbol_name, address):
>>>     STP_MODULE_NAME_LEN = 128
>>>     STP_SYMBOL_NAME_LEN = 128
>>>
>>>     with open(CTL_CHANNEL_NAME, "wb") as f:
>>>     # STAP_RELOCATE (9)
>>>         f.write(struct.pack('<I', 9))
>>>         write_relocate_string(f, module_name, STP_MODULE_NAME_LEN)
>>>         write_relocate_string(f, symbol_name, STP_SYMBOL_NAME_LEN)
>>>         f.write(struct.pack('<Q', address))
>>>
>>>
>>>
>>> On Thu, Jul 27, 2017 at 7:20 PM, Arkady <arkady.miasnikov@gmail.com>
>>> wrote:
>>> > P.S. Another idea is to use kernel IPC instead of function calls.
>>> > Files, named pipes, sockets, memory mapped files - just about anything
>>> > can do the trick.
>>> >
>>> > On Thu, Jul 27, 2017 at 7:03 PM, Arkady <arkady.miasnikov@gmail.com>
>>> > wrote:
>>> >> Eyal,
>>> >>
>>> >> Utility stap employs the kernel debug information installed in the
>>> >> system. When you load a module command insmod does not update the
>>> >> kernel debug info. There are simple two ways to resolve the issue
>>> >> *  Load the module, get the address of the function foo using
>>> >> /proc/kallsyms, provide the address of the foo as an argument to the
>>> >> STAP script.
>>> >> *  Link the module statically with the kernel and update the
>>> >> kernel-debuginfo
>>> >>
>>> >> Arkady
>>> >>
>>> >> On Thu, Jul 27, 2017 at 5:47 PM, Eyal Yehuda via systemtap
>>> >> <systemtap@sourceware.org> wrote:
>>> >>>
>>> >>>
>>> >>> hello
>>> >>>
>>> >>> The
>>> >>>  issue I am facing is of undefined symbols in system tap kernel module
>>> >>> when trying to link to another kernel module with exported symbol
>>> >>>
>>> >>> please note environment setup:
>>> >>> os:  debian 9 stretch 64bit
>>> >>> kernel version:  4.9.0-3-amd64
>>> >>>
>>> >>>
>>> >>>           I created the following simple systemtap script using guru
>>> >>> mode
>>> >>>
>>> >>>           system tap script:      temp.stp
>>> >>>
>>> >>>
>>> >>>          %{
>>> >>>                  extern int foo(void);
>>> >>>          %}
>>> >>>
>>> >>>           function call_foo:long() %{/* pure */
>>> >>>                   STAP_RETVALUE = foo();
>>> >>>          %}
>>> >>>
>>> >>>           probe syscall.open {
>>> >>>                  printf("foo() : %d\n",  call_foo())
>>> >>>           }
>>> >>>
>>> >>>
>>> >>>
>>> >>>
>>> >>>  In addition to that I created the following simple kernel module with
>>> >>> an exported symbol function to be used from inside system tap
>>> >>> script
>>> >>>
>>> >>>          kernel module:       xxx.c
>>> >>>
>>> >>>          #include <linux/kernel.h>
>>> >>>          #include <linux/module.h>
>>> >>>          #include <linux/printk.h>
>>> >>>
>>> >>>          static int foo(void){
>>> >>>                  pr_info("foo()\n"); return 0;
>>> >>>          }
>>> >>>          EXPORT_SYMBOL(foo);
>>> >>>
>>> >>>          static int __init xxx_init(void){
>>> >>>                 pr_info("xxx_init()\n");
>>> >>>            return 0;
>>> >>>          }
>>> >>>
>>> >>>          static void __exit xxx_exit(void){
>>> >>>                 pr_info("xxx_exit() \n");
>>> >>>          }
>>> >>>
>>> >>>          module_init(xxx_init);
>>> >>>          module_exit(xxx_exit);
>>> >>>          MODULE_LICENSE("GPL");
>>> >>>
>>> >>>
>>> >>>          After compiling the kernel module and insmoding it, I run the
>>> >>> command to compile systemtap script as follow:
>>> >>>          stap -gk -v temp.stp
>>> >>>
>>> >>>          the compilation command result with the following error:
>>> >>>
>>> >>>
>>> >>>  Pass 1: parsed user script and 465 library scripts using
>>> >>> 113912virt/46752res/6476shr/40564data kb, in 110usr/20sys/124real ms.
>>> >>>
>>> >>>  Pass 2: analyzed script: 2 probes, 2 functions, 99 embeds, 0 globals
>>> >>> using 165912virt/100212res/7716shr/92564data kb, in
>>> >>> 680usr/50sys/731real
>>> >>>  ms.
>>> >>>
>>> >>>  Pass 3: translated to C into "/tmp/stapzKUZ11/stap_1837_src.c" using
>>> >>> 165912virt/100404res/7908shr/92564data kb, in 10usr/10sys/9real ms.
>>> >>>          WARNING: "foo" [/tmp/stapzKUZ11/stap_1837.ko] undefined!
>>> >>>          Pass 4: compiled C into "stap_1837.ko" in
>>> >>> 1410usr/120sys/1963real ms.
>>> >>>          Pass 5: starting run.
>>> >>>          ERROR: Couldn't insert module '/tmp/stapzKUZ11/stap_1837.ko':
>>> >>> Invalid parameters
>>> >>>          WARNING: /usr/bin/staprun exited with status: 1
>>> >>>          Pass 5: run completed in 0usr/0sys/16real ms.
>>> >>>          Pass 5: run failed.  [man error::pass5]
>>> >>>          Tip: /usr/share/doc/systemtap/README.Debian should help you
>>> >>> get started.
>>> >>>          Keeping temporary directory "/tmp/stapzKUZ11"
>>> >>>
>>> >>>
>>> >>>          in dmesg I can see the following lines
>>> >>>
>>> >>>          Jul 27 03:56:14 debian9 kernel: [ 3938.166906] stap_2230: no
>>> >>> symbol version for foo
>>> >>>          Jul 27 03:56:14 debian9 kernel: [ 3938.166908] stap_2230:
>>> >>> Unknown symbol foo (err -22)
>>> >>>
>>> >>>
>>> >>>          I also checked /proc/kallsyms
>>> >>>
>>> >>>
>>> >>>          cat /proc/kallsyms | grep xxx
>>> >>>          ffffffffc0584000 T foo    [xxx]
>>> >>>          ffffffffc0584014 t xxx_exit    [xxx]
>>> >>>          ffffffffc0585030 r __ksymtab_foo    [xxx]
>>> >>>          ffffffffc058506e r __kstrtab_foo    [xxx]
>>> >>>          ffffffffc0585040 r __kcrctab_foo    [xxx]
>>> >>>          ffffffffc0586000 d __this_module    [xxx]
>>> >>>          ffffffffc0584014 t cleanup_module    [xxx]
>>> >>>
>>> >>>
>>> >>> Please advice
>>> >>> 1.
>>> >>>  what should i do in addition to solve this issue as I must create an
>>> >>> interaction between systemtap script and another kernel module
>>> >>> 2.
>>> >>>  In case this is not feasible can u please offer another alternative
>>> >>> to
>>> >>> make systemtap script use another kernel module services ?
>>> >>>
>>> >>> Thanks eyal yehuda
>>>
>>